CD34 and breast carcinoma: Engraftment of CD34+ hHSCs in sublethally irradiated NOD/SCID/IL2rγKO (NSG) mice, previously shown to result in mature and functional human hematopoietic cells (31), was followed by intracranial implantation of the human brain-homing breast cancer cell line MDA-MB-231/brain (32) (Figure 3A).